Break in loop expression-3, difference in gcc and llvm behaviour

Question

I've noticed the difference in gcc and llvm behaviour with the following code:

$ cat test.c

int main()
{
 for(int i = 0;; ({break;}))
 printf("Hello, worldn");
}

$ clang test.c -pedantic &; ({break;}))
1 warning generated.
Hello, world

$ gcc test.c -std=gnu11 -pedantic &; ({break;}))
test.c:5:21: warning: ISO C forbids braced-groups within expressions [-Wpedantic]
 for(int i = 0;; ({break;}))

So, llvm thinks that this is GNU extension (seems like it really is), but compiles it, and gcc does not, even if the standard is specified as gnu11. Is it a bug?

Answer 1

Yes.
But probably you wanted to know whether it is a bug in LLVM or in GCC. It's a bug in LLVM. You can't use break in a statement expression to break out of a loop that is not in the statement expression. Statement expressions are their own thing; they don't inherit the surrounding context, except that using a goto statement to a label outside the statement expression is permitted.